This invention relates generally to valves and more particularly to a test valve arrangement for calibration of the opening limits of high and/or low pressure cut-off control valves.
Heretofore, similar test valves have been provided for communicating an alterante test fluid source with a valve means to be tested. For example, U.S. Pat. No. 3,817,282 to Peters issued on June 18, 1974 shows a test valve having a plunger mechanism which is operable to block the primary pressure source to allow an alternate test fluid to communicate from the alternate fluid passage into the valve means to be tested. A detachable stinger is utilized to actuate the plunger mechanism into blocking relationship with the primary pressure source as long as the stinger is inserted within the housing of the test valve. Once the stinger is removed, the plunger returns to its normal position allowing communication from the primary pressure source to the control valve and a spring loaded check valve operates to block the alternate fluid passage to fluid pressure from the primary pressure source. The employment of a separate check valve and plunger mechanism in such a test valve arrangement necessitates a relatively large number of elements and the test valve at times can be subject to malfunctioning.
Another example of such a test valve is shown in U.S. Pat. No. 3,987,817 to Peters issued on Oct. 26, 1976 wherein a test valve is disclosed that eliminates the necessity of the separate check valve element. This second patent to Peters is similar to the first in that the test valve utilizes a plunger mounted within a housing which is actuated into a seated position blocking the flow of fluid from a primary pressure source by a hollow stinger which is inserted within the central bore of the housing. The major differences arise in the manner of blocking the alternate fluid passage to fluid pressure from the primary pressure source. U.S. Pat. No. 3,987,817 utilizes a plunger that has an O-ring surrounding its circumference so that when the stinger is removed and the plunger returns to its normal unactuated position the O-ring contacts a restricted diameter portion within the central bore of the housing. The O-ring provides a seal between the plunger and housing thereby blocking the alternate fluid passage to fluid pressure from the primary pressure source. This design provides a general improvement over Peters' first patent due to its simplicity and decrease in number of valve parts, however, it is not applicable to all field service conditions. O-rings do not always provide adequate sealing characteristics, particularly when subjected to high pressure conditions such as in the range of 20,000 p.s.i.
Further, the above described test valves have open conduit end plugs which replace the stingers when the test valves are in their unactuated position. This provision allows pressurized fluid in the alternate fluid passage to escape to the outside atmosphere. Also, if the check valve or O-ring leak, then fluid from the primary pressure source vents to the outside atmosphere. In certain service conditions it is undesirable to allow fluids in the primary pressure source to come into contact with the outside atmosphere particularly where such fluid is flammable or harmful to man or the environment.
It is, accordingly, a general object of the invention to provide a high pressure in-line test valve which remains in position and normally communicates a first fluid pressure source with the control valve means to be tested, but which test valve is constructed and arranged so that communication between the first fluid pressure source and the valve means to be tested can be blocked off and to thereafter enable an alternate fluid pressure source externally of the test valve to be conducted to the valve means for testing thereof. Upon completion of the testing of the valve means, the test valve is constructed and arranged so that it blocks off communication between the alternate fluid pressure source and the valve means being tested with a dual sealing system so that no fluid is allowed to escape from the test valve to the outside atmosphere. The test valve further being constructed and arranged so that it will automatically reestablish communication between the first fluid pressure source and the control valves upon completion of testing.
Another object of the invention is to provide a high pressure in-line test valve that is capable of withstanding working pressures of 20,000 pounds per square inch without leaking fluid externally of the test valve.
Yet, another object of the invention is to provide a high pressure in-line test valve that utilizes an automatic dual sealing arrangement to block the alternate fluid passage from the working pressure existing in the first fluid pressure source to prevent any leakage of fluid through the alternate fluid passage to the exterior of the test valve.
Other objects, advantages and novel features of the invention will be apparent to those of ordinary skill in the art upon examination of the following description of a preferred embodiment of the invention and the accompanying drawings.